Medicaid is the nation's largest health care program for poor and disabled Americans with chronic illness, and rates of mental disorders are more than twice as high among Medicaid recipients as in the general population. However, little is known about the impact of mental comorbidity on quality of care for chronic conditions within the Medicaid system, how that association varies across different mental diagnoses, or how is moderated by patient, provider, and system-level factors. The recent release of standardized 50-state Medicaid Analytic Extract (MAX) Files makes it possible, for the first time, to study the relationship between chronic conditions and mental comorbidity within the national Medicaid system. We propose a study using 50-state Medicaid claims data to examine the implications of mental comorbidity for quality of care among Medicaid recipients with one of three chronic conditions --diabetes, heart disease, and asthma. County-level provider and demographic characteristics and state-level Medicaid policy parameters will be merged from other data sources. The application proposes to 1. Study how different comorbid mental conditions are associated with quality of care for the three chronic medical conditions. Analyses will examine both underuse of evidence- based services using HEDIS indicators and overuse, as reflected by use of Emergency Room and Inpatient services for ambulatory-sensitive conditions. 2. Examine how the association between mental disorders and quality of care is moderated by patient, provider, regional and Medicaid policy factors, and mediated by use of outpatient medical services. This study will provide the first national description of the impact of mental comorbidity on quality of care in the Medicaid program, how it differs across particular mental conditions, and how it is influenced by patient, provider, and system-level contextual factors. Better understanding the impact of mental comorbidity among Medicaid recipients can provide critical information for state and federal policymakers, public sector providers, and patients. It will also help to more broadly illuminate the relationship between comorbid conditions and quality of medical care in poor and vulnerable populations. Project Narrative Although Medicaid is a critical health care program for poor and disabled Americans with chronic physical and mental illnesses, little is known about the impact of mental comorbidity on quality of general medical care within the Medicaid system. The proposed study will use Medicaid claims data from all 50 US States to examine the impact of mental comorbidity on quality of care among Medicaid recipients with one of three chronic conditions--diabetes, heart disease, and asthma. Better understanding the impact of mental comorbidity among Medicaid recipients can provide critical information for state and federal policymakers, public sector providers, and patients.